How do I specify the default "public" group? The string "public" doesn't seem to work.

A lookup group is a string used to identify a set of services.
The default group is called the "public" group, but when you
want to use this default group in your code you need to specify
a null string as its name. The string "public" is actually a valid group
name, but is does not refer to the default public group.

Advertiser Disclosure:
Some of the products that appear on this site are from companies from which QuinStreet receives compensation. This compensation may impact how and where products appear on this site including, for example, the order in which they appear. QuinStreet does not include all companies or all types of products available in the marketplace.